1981 Custom Race Catamaran

[Corysprouts84]

Just picked up a piece of history. Im sure a lot of you know the boat. I know a little about it. But more importantly. Its time to power it. I started looking at big blocks and realized i dont want to drop 40k on #6 drives so im going to convert the boat over to double or trip outboards. I figure the weights should be pretty close. The boat originally had 2 - 525s with #6 drives if im not mistaken. Boat weighs in around 4300#'s not rigged. Im looking at 300 hp yamaha hdpi outboards. I dont want the boat to get swamped out by wakes but also dont want to under power. Any advice? Also im a newbie. Be gentle. My last boat was a 29' fountain with 2- 540s. So the race cat is a new adventure. 443233443234

[Dave S]

Why not go BBC and brvos?.....just askin.....boat ready for castion.....motors.......I like obs but.......?

[kellytheaker]

I had the same initial thought on big blocks and thought it may be cheaper . I was also stoked about the history as well and your enthusiasm . Cool look n- build thread ? Keep it on budget go inboard and bravo . You asked didn' yah so I'm with above - your build though - I have enough just rigging my own stuff. Have fun paint or overlay looks fantastic and it' was #1 - so can' go wrong with it just sitting in the driveway - putting in the garage is another .so I don' know the boat or history so lets hear it . This stuff is way out of my vision for the small lake I'm on .

[JPEROG]

3 300XS motors will be your best bang for the buck. It still will not be cheap to rig. Make sure that you get offshore clamp assys., side ram steering, and add a water diverter in the tunnel for the middle motor. Its easy to pull the motors and sell them separate rather then to try and sell what most will consider an under powered cat with old bravo drives (which you are guaranteed to break in time).

Joe

[Dave S]

Ya but the tralll of brxonen.promises... 300xs moters will give ya a pale look at the ckeypoint....JMO....BBC forever....HeeHee....big boat big power.....AskZJulllel....**** dammm any one with big boats big power.... JMO...Richy Zull......

[Corysprouts84]

I was looking at horsepower/torque. Not a huge difference between the yamahas and xs. Just price. What kinda speed do you think with 900 hp.

[Corysprouts84]

The boat was built for al copeland by allen brown al copeland was the owner of popeyes. Boat pulled 144 mph in its day.

[Corysprouts84]

Jperog i was looking at doing jack plates. Do you think i should do something different?

[AZMIDLYF]

NIZPRO...30ft AMT down under running in offshore circuit.

443289

[JPEROG]

Jperog i was looking at doing jack plates. Do you think i should do something different?

For budget purposes I would go with simple 6" or 8" Z lock jack plates and bungee your motors down. I always ran the center motor 3 1/2" higher then the outsides so drill your mounting holes accordingly. Like you have figured out, to go big power cost big money and you would potentially loose in repairs and resale more then you will pay for the outboards. I am speaking from experience "outboard parts always sell if you want to liquidate them". You should have a low to mid 90's boat that will be dependable and use a reasonable amount of fuel. Cool project-Al will never be replaced that is for sure-his old 46 cougar V-bottom was converted to a pleasure boat up in Michigan and makes me smile every time I see it.

Joe

[Turborr]

Yamaha hpdi's 300 were plagued with problems and are weak for 300's. Thats why you will see them for sale cheap. Minimum I would go with is 3 300xs's. Triple promax's or x's can work also but make sure you have huge tanks and gas stations close....not even talking about $.

[Corysprouts84]

The guy had these hdpis on a 12,000lb cc fishing boat pulling 40s-50s. Im less than half that weight. Ive heard about the issues. Engines are around 6-700 hrs good compression with all rigging and steering for 7500. Still dont think its worth it Turborr?

[Turborr]

When I was looking for engines for my boat I was looking at the same thing that you were looking at. I went with the 300xs's because a boat like mine rigged with the hpdi's ran about 15 mph less than one with the xs's. On a cat especially, you need the power to get it up on that cushion of air because if you dont you will have a bow-plowing, porposing not fun ride. You will need all the power you can get. What length is that boat?

[Corysprouts84]

When I was looking for engines for my boat I was looking at the same thing that you were looking at. I went with the 300xs's because a boat like mine rigged with the hpdi's ran about 15 mph less than one with the xs's. On a cat especially, you need the power to get it up on that cushion of air because if you dont you will have a bow-plowing, porposing not fun ride. You will need all the power you can get. What length is that boat?
31'

[Turborr]

Still saying triple 300xs's are the ticket. Another option is 250xs's. They are strong 250's more like 270hp. I will take the 250xs over the 300hpdi's. That 31 will run good with the tripps.

[JPEROG]

Still saying triple 300xs's are the ticket. Another option is 250xs's. They are strong 250's more like 270hp. I will take the 250xs over the 300hpdi's. That 31 will run good with the tripps.

As he has said, don't go with anything other then 300XS (offshore clamps and sportmasters). It will be the least expensive route (both initial set up and operational/repair cost) by far. You are going to surface the gear cases on this rig and unless you have a container full of coned Yamaha cases at your disposal then that aspect alone should make your decision an easy one.

Joe

[Corysprouts84]

Yeah i agree. Im definitely looking at triples. I found a few evinrude 225s or 250s

[JPEROG]

I don't know if you are understanding what people are trying to advise you on. There is not another motor that is strong enough to handle the beating that you will put these motors through. Going with anything other then Mercury offshore motors is going to be a major headache and major amounts of downtime for constant parts replacement. The biggest factors are clamp assembles, motor mounts and gear cases-its not if, its when and how often you will break them. Steering components and availability also become an issue for brands outside of Mercury (you want side rams and wing plates- No front mount for what you are building). If you weren't required to surface the cases then you would have other options.

Coming from someone that has done what you are doing: Don't rush it and do it right- You will be much happier and have a lot more enjoyable running. I am not trying to be a jerk, just trying to save from walking into a trap that will consume you with grief, financial burden, lack of re-sale ability, and less then optimum performance results.

Joe

[Corysprouts84]

Thanks joe, JPerog i really appreciate the help. I dont know much about it. Ive always been a v hull guy with big blocks. What do you mean by surface the cases.

[Corysprouts84]

Jperog,
If i was to stick with big blocks how much horsepower do you think i would need for a comfortable efficient ride. Mercury makes the 300 verado supercharged 4 stroke. They have a lot of good reviews. Whats the difference between them and the xs?
Thanks.

[Turborr]

Thanks joe, JPerog i really appreciate the help. I dont know much about it. Ive always been a v hull guy with big blocks. What do you mean by surface the cases.

On a cat when you are running at higher speeds most of the gearcase is actually out of the water. Only the bottom of the bullet skims the surface of the water hence the term surfacing the gearcase.

https://www.youtube.com/watch?v=e2Aesk4fMh4

Take a look at that for example. I have seen them run higher than that...

[Corysprouts84]

On a cat when you are running at higher speeds most of the gearcase is actually out of the water. Only the bottom of the bullet skims the surface of the water hence the term surfacing the gearcase.

https://www.youtube.com/watch?v=e2Aesk4fMh4

Take a look at that for example. I have seen them run higher than that...

Thanks Turborr